The Necromancer's Path.

I discovered an interesting thing. A secondary hero from Giovanni ran through the Ghost Gorge and found a cloak and a dragon skull there. So, I didn't have to go there myself... It's clear that the ghosts didn't attack him...

(I'm not the map author, but I'll answer.)

You can get both the cloak and the skull even in the first week. I'm attaching a screenshot showing how to do it: it's better to go along the white squares and not enter the green ones (the ghosts will attack).
If the author is against it, I'll delete the screenshot, although you can figure it out yourself by trial and error (getting to the skull without fighting).